Pipe fittings of thermoplastic synthetic resins can be produced by injection molding processes in dies or molding tools having separable outer die members and a die core. At least at one end of the injection molded fitting it is advantageous to provide an inwardly open groove for insertion of a sealing material or ring in the assembly of the fitting into a piping system. This inwardly open groove is formed by an annular bead on the core which, for removal of the injection molded article, may be divided into segments which can be retracted into the interior of the die core.
In earlier systems for this purpose, a complex mechanism was required in the core and this mechanism had to be fabricated at high cost, took up considerable space and, therefore, could only be used for large core diameters or large internal diameter pipe fittings.